This invention relates to a device for axially securing a moving blade and for eliminating rotor unbalances in the case of axial-flow compressors or turbines of gas turbine engines, in which the moving blades are anchored by means of their blade bases on axial grooves of a wheel disk distributed along the circumference. Each axial groove encloses an indentation formed between the groove bottom and the base end.
A known device of this type is described in European Patent document EP-A 0437 977. The moving blade operates as an axial securing device of an unbalance weight, which only in specific cases can be anchored by means of its exterior edge end on a recess of the blade base. The moving blade is approximately crescent-shaped in its cross-section. In this case, the unbalance weight is situated in an indentation between the base end and the groove bottom closed by the blade base on one side. All moving blades are secured only in one axial direction by a snap ring which circumferentially extends on the outside between the wheel rim and the blade base ends. The snap ring engages in this case on the upper end in grooves of axially projecting projections of the blade bases.
When a local disk unbalance or rotor unbalance is determined, the axial securing must first be released and a concerned moving blade must be pulled out of the axial groove in order to be able to push the weight, together with the blade, into the axial groove. The one-sided axial blade securing and the weight arrangement, which can be secured on the blade, require a relatively expensive and costly fastening of the blade.
A device for axially securing blades known from German Patent document DE-AS 10 51 286 requires a complicated blade construction, particularly with a base-side contact flange by means of which the blade is axially secured in one direction on a side of the wheel rim. For securing in the other axial direction, the prior art provides a strip constructed as a spring steel sheet. Before the installation of the blade, the strip is inserted in an axial flute on the groove bottom. The flute forms a one-sided indentation which is expanded in a diverging manner toward one wheel rim side. In the position of the strip which is pressed down with respect to the indentation, the blade is slid from one side into the axial groove. In a recess area of the contact flange, the strip, which springs upward radially out of the indentation, forms a bent stop which axially secures the blade in the other direction. Another bent stop of the strip secures it on the wheel rim on the side facing away from the indentation. In the prior art, no compensation is provided with respect to unbalances. This also applies to alternatives of the known case, according to which, for example, the flute encloses a uniform indentation along its whole length and the spring strip has a downwardly directed U-shaped right-angle bend.